ICEFLEX® IEC SHF2 - Halogen free New

High mobility of the molecular segments in a polymer is the condition for the rubbery state, i.e. high elastic elongation. With decreasing temperature, those movements are going to be frozen until the material becomes stiff, brittle and will crack by bending. This means that it is no longer useful as a ‘rubber’. This temperature is called the glass transition temperature (Tg).

This is the dominating phenomenon to understand the behavior of rubbers in cold conditions.

Typical temperature modulus curve for polymer

EVA-based sheath (ethylene vinyl acetate copolymer) is a multi-functional elastomer, which resists the deteriorating influences of oil, heat and weathering agression. This rubber is also combined with other components to produce fire retardant, low smoke products to avoid emission of acid gases in fire conditions leading to corrosion damage.

It is noticeable that both the insulation and sheathing materials are thermosets. These products are cured or hardened into a permanent shape. The curing is a non-reversible chemical reaction also known as cross-linking which usually occurs under heat. The cross-linking that occurs during the curing reaction is brought by linking of atoms between or across two linear polymers resulting in a three-dimensional rigid chemical structure. Conversely to thermoplastics that are softened or melted when heated to a flowable state, rubber cross-linked products can resist to temperature overshot without any damage.

Schematic representation of a polymer network

Cold behaviour

• determine physical and chemical parameters of raw materials (glass-transition temperature, melting point…);
• measure macroscopic properties with standardized techniques (brittleness, elastic recovery, stiffness, hardness…) ;
• qualify the final cable products.

Final certification for the cold behavior was done by Lloyd’s Register according to the well recognized Canadian standard CSA 22.2.

The cable specimen and a mandrel are conditioned at -50°C for 4 hours. The specimen is then slowly bent around the mandrel at a uniform rate speed. At the end of the procedure, the test piece is examined while still on the mandrel. Neither the insulation nor the jacket shall crack or rupture after the bending operation.

Comparative pictures after bending test:

The apparatus consists of a vertical tracking device for the impact component or hammer. After 4 hours period in a cold chamber at -45°C, the cables are submitted to the impact of the hammer from a height of 915 mm.

Neither the insulation nor the jacket, on at least 8 out of 10 specimens shall crack or rupture when the cable is subjected to an impact test.

Comparative pictures after impact test :